This invention involves a method by which the pressure-drop energy from a pressurized gas stream in a pressure regulation process can be recovered and reused so as to reduce and eliminate a temperature drop occurred spontaneously at the downstream of the pressurized gas, an apparatus by which the said process can be finished through a creation of a gaseous wave system to recover the pressure-drop energy and convert it into the form of heat being returned into the pressurized gas stream during the said pressure regulation process, and a pressure recovery system which is designed for a high pressure drop process to recover the pressure drop energy in the form of heat through heat exchanger units so as to return the heat into working stream being regulated or to be used for the other process. The mechanism in the present invention allows the pressure-drop energy, usually wasted in traditional pressure regulating processes, to be used in the form of heat, which can either be returned into the pressurized stream against the temperature drop or extracted from the gas stream. The application of the present invention is intended for a pressure energy recovery system in natural gas liquefaction plants, natural gas distributing regulation stations, and relative petrochemical industrial processes where the pressure regulation process is needed in order to meet the requirement of operating pressure conditions but where a temperature drop caused by the pressure regulation processes is unacceptable. In contrast with all prior arts used in pressure regulation processes, so called pressure regulators, the present invention has a unique feature in that the pressure-drop energy in conventional pressure regulators is used to produce a periodic gas resonant flow and wave interactions inside the device of the present invention, so that a heat effect is generated and reused in flow fluctuation conditions (either pressure drop or flow rate). This device is thus called a gaseous wave pressure regulator (GWPR) due to its operating features. By entirely operating under the unique mechanism, GWPR can recover the pressure energy loss in traditional pressure regulators which are now widely used in a variety of industries, and replace them to reduce energy loss and increase the efficiency of system operations in natural gas and petrochemical industries.
Potential applications of the present invention can be found in a wide range of industrial fields where pressure regulation processes are required. For instance, in petrochemical industries, numerous pressurized gas regulating processes are involved in processing operations such as condensation, separation, liquefaction, the delivering and redistributing of pressurized gas streams, vaporization and combustion of liquid gas, gas stream refining and distilling, etc.
No matter what pressure regulating processes are involved, generally speaking, all are operated under specific pressure conditions in order to meet two fundamental goals, i.e., 1) the optimization of the system performance and 2) maximization of production. Pressure regulation processes are defined here as the common measure to adjust the operated system in different pressure stages and to keep system operations in the proper condition. From the point of view of thermodynamics, all the pressure regulating processes are for two main purposes: (1) to obtain a cooling effect which is generated by the temperature drop from the pressure drop, and (2) to adjust the pressure level which fits the proper pressure operating condition for the optimized performance of the systems. The former is achieved by using either the pressure energy extracting devices such as gas expanders, or Joule-Thomson effect, such as throttling valves etc., between the pressure drop. The latter is completed only by using pressure regulation valves, so called pressure regulators, to regain the energy loss in such processes.
However, the pressure regulating devices used currently are all limited by some fundamental imperfections in their operation mechanism. The main difficulty in avoiding the loss of the pressure energy within devices, is to recover or extract the pressure-drop energy from pressure regulating processes which normally involves the structure with mechanical moving parts and reduces the reliability of system operations. As a result, in the normal industrial practice, this part of pressure energy is simply wasted, dissipated by flow friction and turbulence, because the current pressure regulating devices cannot recover the energy and maintain the simplicity and reliability of the operating system at the same time.
More specifically, in the pressure regulating processes, pressurized gas streams undergo in essence a steady Joule-Thomson process (J-T effect) to reduce the pressure level without heat and work transfer. The portion of energy in pressure drop is entirely dissipated during stream flows through pressure regulators. As a result, pressure regulation processes will bring about the energy loss between the pressure drop and the temperature change. This is due to the internal energy reduction and entropy increment which depends on the operating condition. The temperature effect along with the pressure drop is generally represented by the Joule-Thomson coefficient .mu..sub.JT defined by ##EQU1## which indicates the change in temperature due to a change in pressure at constant enthalpy. For a temperature increase during the pressure regulation, the Joule-Thomson coefficient is negative; for a temperature decrease, the Joule-Thomson coefficient is positive. Most of the pressurized gases used in the industrial system are imperfect gases with a higher inverse temperature above atmosphere, except for hydrogen and helium gases. Therefore, it is very common that a temperature drop accompanied with the pressure regulation process downstream of the pressurized gas can be observed in most industrial systems.
Unfortunately, all the current pressure regulating devices can not work without the generation of this spontaneous temperature drop although it is unexpected in the pressure regulation processes and not allowed by the certain process operations. The consequence of the temperature drop in some industrial processes can be very serious. It may lead to reduce production and system liability or lower system efficiency.
Usually, in order to overcome this inefficiency, additional processes and equipment are required to eliminate this temperature drop to reduce overall potential damage in the operation and the maintenance cost of systems. On the other hand, the cost will be added up due to the operation and maintenance of the additional processes and equipment. For instance, in the natural gas industry supplying natural gases from gas fields are delivered by the pipeline under a pressure level higher than the operating condition of an LNG operating plant and commercial residential area in the consideration of economical transportation. Before the supplying gas steam enters the utility network or LNG plants, a pressure regulation is required to reduce the stream pressure. A typical process diagram between a gas supply pipe and an LNG operating plant is shown in FIG. 4A.
As shown in FIG. 4A, before entering an LNG plant, a supply of natural gas has to pass through several pressure regulators to reduce the pressure level. This is necessary in fitting the pressure operating condition either to the LNG plant to be liquefied or to the residential distribution system. In both cases, the range of pressure drop passing the pressure regulator is around .DELTA.P.apprxeq.300.about.700 psi, which is a significant pressure energy loss. On the other hand, since the pressurized gas stream reduces its temperature after the regulation, it results in two undesirable consequences to affect the LNG or gas distribution operation. Firstly, for the stream entering the LNG plant, some components of light hydrocarbon and water contained in supplying the pressurized gas stream will become partially vaporized which is in a liquid state and results in the overloading of the dehydrated unit and molecular seize absorbers. Malfunction in the operation of dehydrated devices such as molecular seize and absorbers in the early stage of the LNG plant, will reduce the LNG production and affect the reliability of the system's operation. Secondly, for the stream distributed into the residential system, the pressure drop between the distribution stations and the supplying pressurized stream is so great that it will result in the partial condensation of light hydrocarbon components as well.
In consequence of a temperature drop after pressure regulations, condensed light hydrocarbon components in the distribution pipeline will reduce the heat capacity or caloric value of natural gas, and the temperature drop also leads to the regulator being rusty in the summer and fully iced in the winter season, since the vapors in the atmosphere are condensed and accumulated on the regulators. In order to overcome the problem resulting in the temperature drop within the necessary pressure regulating processes, usually, in LNG industrial practices, additional heating devices, such as oil burners or electric heaters, are used to reheat the supplying pressurized gas stream before or after it passed through the pressure regulator. It is clear from this example that since the flowing volume heated is so great and the fuel or electricity cost to operate the reheating process is so huge, the amount of pressure energy loss is extremely significant.
Similar processes with double cost in both pressure energy waste and additional reheating bills attached to pressure regulations can also be found in other industrial processes and systems, where pressurized gas is delivered as fuel in a high pressure level and used in a lower pressure level--in all these cases, energy is lost and expenses increases.
Unfortunately, since pressure regulation methods and devices are so widely used in a variety of industrial processes, during the last few decades, a great deal of effort has been concentrated on the device performance based on the development of new technology without addressing the problem of energy loss and the negative consequence of temperature drop in the pressure regulator. In all previous arts, the progress and improvements have been focused on the mechanism design and controllability of pressure regulators to fit in with the specific operation condition and processes, as were employed by U.S. Pat. Nos. (5,810,029, 5,797,425, 5,787,925, 5,740,833, 5,697,398, 5,657,787, 5,507,308, 5,458,001, 5,402,820, 5,392,825, 5,131,425, 5,047,965, 4,974,630, 4,974,629, 4,971,108, 4,966,183, 4,874,011, 4,840,195, 4,817,664, 4,811,755, 4,757,839, 4,684,080, 4,679,582, 4,606,371, 4,546,752, 4,503,883, 4,332,549, 4,111,222, 4,067,355, 4,067,354, 3,989,060, 3,971,410, 3,845,780, 3,841,303, 3,773,071, 3,698,425, 3,675,678, 3,665,956, 3,648,727, 3,623,506, 3,580,271).
Before discussing the issue of energy loss in the traditional pressure regulators, a brief summary in the previous arts seems necessary so that the significance of the present invention can be viewed more clearly.
In U.S. Pat. No. 5,810,029, an anti-icing design is provided for a gas pressure regulator to prevent normal pressure regulator device from icing used as outside gas pressure regulator, which has a pressure vent and a downwardly opening vent tube associated with a skirt connected to and surrounding the vent tube. In this art, the mechanism design prevents rain or freezing rain from splashing back upwardly into the passage. In U.S. Pat. No. 5,797,425, a three-stage gas pressure regulator is provided in which a supplementary pressure regulator is used with conventional single or multi-stage pressure regulators with a novel two stage balanced pressure regulator to form a three-stage vacuum demand pressure regulation system in order to regulate the pressure of compressed gases used as fuel in engines, such as natural gas used in natural gas powered vehicles, especially useful in mono-, bi-, and dual fuel engine applications.
In U.S. Pat. No. 5,787,925, a pneumatically served gas pressure regulator is accomplished providing a relatively wide range of gas flow rates with precision outlet pressure control with a dome loaded gas pressure regulator and a pressure sensor controller integrated in a single unit. In U.S. Pat. No. 5,740,833, a two stage gas pressure regulator with a body housing having a gas inlet and a gas outlet, and a common interior wall dividing the body housing into two chambers forming two pressure reducing stages is given to accomplish the multi-stage regulation of pressurized gas stream. In U.S. Pat. No. 5,697,398, a method of manufacturing a diaphragm assembly for a fluid pressure regulator is introduced, including a disk for regulating the flow of fluid through an orifice and a valve stem attached to the disk. In U.S. Pat. No. 5,657,787, a gas pressure regulator is designed consisting of a body member which mounts a valve between the inlet and outlet gas passages, and also a tubular sleeve which communicates with the outlet passage. In U.S. Pat. No. 5,507,308, a gas pressure regulator is introduced with a piston, a hollow rod, a high pressure chamber, an internal chamber, and coacting with a valve seat. This invented regulator is useful in respiratory equipment for divers, particularly for divers in cold water.
U.S. Pat. No. 5,458,001 shows a gas pressure regulator and a diaphragm assembly which enables the precise alignment of a diaphragm and a valve carried thereby with respect to a valve seat for improved regulator performance. U.S. Pat. No. 5,402,820 shows a stabilizer for fluid pressure regulators enhancing regulator stability without affecting the regulator capacity. U.S. Pat. No. 5,392,825 uses a gas pressure regulator for regulating the output pressure of a gas from a pressurized gas cylinder, including a flashback assembly disposed at the gas outlet of the pressure regulator to reduce the possibility of migration of a flashback upstream from the torch and hose into the pressure regulator. U.S. Pat. No. 5,131,425 represents an improvement in a gas pressure regulator. It has an inlet, an outlet, a gas flow passage, and a regulator mechanism in the valve body, including a relief valve which is set to open when the pressure of the gas in the flow passage exceeds a predetermined pressure.
In U.S. Pat. No. 5,047,965, a microprocessor controlled gas pressure regulator provides an adjustment of a gas regulator valve, having a spring based diaphragm controlled pilot valve which is automatically affected by supplying augmenting pressure to the spring side of the diaphragm via an electrically adjustable regulator valve under the control of a local microprocessor. In U.S. Pat. No. 4,974,630, a gas pressure regulator with a throttle valve is introduced in which the throttle valve has a sealing plug comprised of a needle and a base float fluidically drafted for closing a truncated cone hole of the throttle valve. U.S. Pat. No. 4,974,629 is a gas pressure regulator for saving a resetting operation, which includes a throttle valve provided between a gas inlet passage having an orifice formed therein and a pressure sensing chamber pertaining to a gas exit passage.
Scanning over the previous arts within U.S. Pat. Nos. 4,971,108, 4,966,183, 4,874,011, 4,840,195, 4,817,664, 4,811,755, 4,757,839, 4,684,080, 4,679,582, 4,606,371, 4,546,752, 4,503,883, 4,332,549, 4,111,222, 4,067,355, 4,067,354, 3,989,060, 3,971,410, 3,845,780, 3,841,303, 3,773,071, 3,698,425, 3,675,678, 3,665,956, 3,648,727, 3,623,506, and 3,580,271, it can be concluded that all pressure regulators introduced here have the similar mechanism: they use regulating pressure to adjust the pressure level by throttling pressurized gas stream in the configured chamber or passage, even though they may be used in dissimilar controlling manners (diagram, mechanical level, actuators, etc.) specialized for specific operating conditions and industrial applications.
Obviously, the prior arts have made significant improvements and progress in terms of a pressure regulator for manipulation and controllability, but none have made significant improvement on the purpose of utilizing and recovering pressure drop energy from pressure regulation processes. None of previous arts have made a contribution on the design of a pressure regulator to reduce or eliminate the spontaneous temperature effects which are undesirable and harmful to some industrial processes and systems, associated with the pressure regulating operation. Although there are several forms of pressure regulators used for pressure drop regulation processes shown in prior arts, there was hardly any type of regulator which can be used as a pressure energy recovery device during the regulating pressure drop to reheat the pressurized gas stream and to increase the stream temperature as well. Therefore, the limitations and incapacity of the previous arts have given rise to the significance of the present invention in offering a solution to the energy loss problem in the regulating process.
By contrast with the traditional pressure regulation method and devices aforementioned, the present invention, for its primary object, introduces a method and a device using the mechanism of gas wave interaction during the pressure regulation processes to recover pressure drop energy. The said method and device for pressure regulation in the present invention transfers the pressure drop energy from the regulated pressurized-gas stream into a form of heat inside the device and returns it by reheating the pressurized-gas stream after pressure regulation to compensate for the spontaneous temperature drop. The applicant's apparatus will provide a steady effective operation based on such special operating mechanism of oscillation flow. In its turn, the flow is produced by compressible gaseous waves driven by the pressure drop energy in a designed structure for such an aim to effectively recover pressure energy dispersed in pressure regulation without involvement of any mechanical moving parts. Such a method and the present invented device is especially suitable for special technical processes in energy and chemical industries where the pressure drop regulation of providing pressurized gas streams are needed but the spontaneous temperature drop is unacceptable or harmful for the systems operation. Following the aforesaid example, the original oil burner heating a natural gas stream to prevent temperature drop from pressure regulation shown in FIG. 4A, can be removed after using the present invented device as shown in FIG. 4B.
Therefore, the present invention using the gaseous wave pressure regulating method is able to provide an effective method for industrial processes to regulate the pressure operating condition and to recover the pressure drop energy loss without the negative temperature drop effect. With a view to such a purpose, the present invention aims at meeting several important objectives of its industrial application.
The first is to provide a gas wave pressure regulation method and apparatus to replace the traditional pressure regulators to meet the requirement of operating conditions of the industrial system without the undesirable temperature drop.
The second is to provide a gas wave pressure regulation method and apparatus for petrochemical industries to recover the energy in a high pressure drop from the conventional pressure regulation processes and reuse the recovered energy in the form of heat in the systems to compensate for the energy loss in the source to elevate the pressure level of the pressurized gas stream.
The third is to provide a wave pressure regulation method and apparatus for the LNG operating plant to be used in the gas supply inlet where the pressure regulation is needed to adjust the supplying pressure fit to the pressure condition of the operation plant and to avoid using additional reheating equipment.
The fourth is to provide a gas wave pressure regulation method and apparatus for a natural gas regulating station between gas supply pipeline and residential network to reuse the waste pressure drop energy during the pressure regulation process to avoid the light hydrocarbon condensation, regulator damage by icing, or rust due to the temperature drop with the pressure regulation.
The fifth is to provide a gas wave pressure regulation method and apparatus for the LNG fuel vaporized system in the LNG vehicle to recover the pressure energy from the vaporization process of LNG fuel and increase the engine efficiency by reheating the gas fuel before combustion is generated from the recovered pressure energy.
The sixth is to provide a gas wave pressure regulation method and apparatus for the fuel vaporized system of liquid gaseous fuel for rocket engines to increase the engine's efficiency by increasing the temperature of injecting gas fuel before the vaporized fuel enters the combustion chamber.
The last objective is to provide a gas wave pressure regulation method and apparatus with an energy recovery system which is able to operate under extreme high pressure drop condition by means of a multi-stage operation of the gaseous wave regulation device in a series to recover the pressure drop energy into the form of heat to be recycled.
With these and other objectives in view, as will be apparent to those skilled in the art, the present invention resides in the combination of parts set forth in the specification and is covered by the claims appended hereto.